Conventionally, in a manufacturing process for a semiconductor device, openings such as contact holes are formed in dielectric layers by plasma etching using a patterned photoresist layer as a mask. However, as device sizes decrease, the size of features such as contact holes is reduced, requiring the replacement of conventionally used resist masks.
A hard mask formed of amorphous or transparent carbon has been used for dry etching of silicon oxide films, which offers high etch selectivity relative to a photoresist or other hard mask materials. However, the use of amorphous carbon as a mask is inapplicable for some processes when plasma etching silicon oxide, in part, because a sufficient selectivity of the silicon oxide film against the amorphous carbon mask cannot be obtained. In addition, etching features in silicon oxide that are 25 nm or less often requires the use of a very thick carbon film, which is generally not extendable for 25 nm patterning due to toppling of the mask structures, making a conventional amorphous carbon mask unsuitable.
It would be useful to provide processes that overcome these or related problems.